candela

[derekleffew]

A Unit of Luminous Intensity, or brightness. From http://physics.nist.gov/cuu/Units/candela.html :

The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 10^12 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.

See also lumen, Foot-candle.

On spec sheets for luminaires, BCP is usually expressed in peak candelas, and performance at any distance may be calculated using the formula
intensity in FootCandles = BCP/distance^2.